Give me the Bad News on Hydraulic Seal Leaks

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SteveHGraham
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Give me the Bad News on Hydraulic Seal Leaks

Post by SteveHGraham »

I feel like this question needs a thread. I am trying to buy a used Kubota, and here is what I learned today: "The seller did say the Kubota tractor has a small hydraulic seal leak but he just keeps an eye on the hydraulic fluid level and tops it off when necessary."

Here's my question: how big a deal is a "small hydraulic seal leak"?

I have never worked on a hydraulic cylinder. I've seen videos where people pop them out, slap new seals on them, and pop them back in, and that makes the whole thing seem insignificant. But I have a feeling not all cases are like that. Maybe something in there could be rubbing something it's not supposed to. Maybe the rod has been abraded in a way that makes it hard to seal. Just guessing.

Input would be appreciated.
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BadDog
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Re: Give me the Bad News on Hydraulic Seal Leaks

Post by BadDog »

Depends on where it is. If it's the loader, then it's an exposed cylinder and easy enough to attack. But they mostly all leak some anyway, so most do as he did, just keep an eye on the fluid until the mess and inconvenience (or function) gets to be enough that rebuilding the cylinder is worth it. You can hire it done, or do it yourself. The gland nuts (or usually wire lock plugs on Kubotas) and mess are usually the worst of it, as long as you don't have scored cylinders. Usually just the seal leaking, and you can just keep using the piston seal itself unless it's gone weak or leaking down.

Likewise the various external plumbing bits sometimes leak hear and there, particularly at the low side return which is external and usually connected across the trans with a rubber hose. Mine was leaking badly there, just needed a new hose that I got for < $10 at the local hose shop (and it's pressure rated, should never go out again). But those return leaks usually only leak when setting, and allow air entrainment (can froth a bit, but hydro oil is resistant to that in moderation) while running. But if it's leaking at the pressure pump, that can get to be a headache depending. My power steering was also leaking into the outer tube housing, filling up to the wheel, then bubbling out the center piece (would be horn on most cars). That was interesting, but an easy fix once I gave them my left testicle and got the kit I needed. Probably could have found standard seals, but that takes time at the local seal/gear house.

But if it's a leak in the 3 point, that can lead you to inventing new curse phrases that have never before uttered by human lips. Shims, pressure specs, balance circuits, the sky is the limit really, particularly if you have a "Grand" with all the fiddly fancy bits. Make a mistake here and it will groan constantly, or jerk and jump so bad you'll swear it's gonna break in half, and has been known to damage 3 point equipment it was so bad.
Russ
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SteveHGraham
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Re: Give me the Bad News on Hydraulic Seal Leaks

Post by SteveHGraham »

So a leaking seal doesn't mean I have to worry about the rod scraping on the gland and ruining itself?
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BadDog
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Re: Give me the Bad News on Hydraulic Seal Leaks

Post by BadDog »

Not normally. But of course things can happen that do score the rod or the bore, and things get a lot worse then. Normal leaking is just sort of weeping past a hard seal, so most let that go quite a long time. My loader cylinders mount inverted, so fluid drains out past the current seals and makes quite a mess, so my short list for this fall when it cools down includes tearing down the main cylinders, carrying relevant parts down the local seal house, and rebuilding them. It doesn't leak all that much, but the mess is killing me...
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SteveHGraham
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Re: Give me the Bad News on Hydraulic Seal Leaks

Post by SteveHGraham »

The seller says he doesn't know where the leak is. He must be rich, because he has it serviced regularly at the dealership. It must not be something scary, or else they would have pushed a profitable repair on him.

The John Deere 430 he wants to sell has a leak at the PTO shaft, but I found an online source for a replacement seal for $9.50. They claim it's easy to install. Not that I would expect them to say it's hard.
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STRR
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Re: Give me the Bad News on Hydraulic Seal Leaks

Post by STRR »

Steve,

Some cylinders are very easy to fix. Pull the pin out of the rod end, loosen the cinch bolt on the rod end, unscrew the rod end, unscrew the cylinder gland, and remove the gland, where the seal is located, by sliding the gland off the rod end. Others are a real pain in the caboose. The rod end is welded on and that makes things much messier. Remove the whole cylinder from the machine. Unscrew the gland, remove the entire rod and piston assembly from the cylinder barrel, unscrew the piston retaining nut, take the piston off, slide the gland off the piston end to get to the seals in the gland. If you have to do all of this, I highly recommend replacing all of the software in the cylinder. Too much work to do for just a small rod seal leak.

When putting either example back together, brass shim stock is your best friend. Wrap some thin shim stock sheet around the rod end to slide the seals over. Grease/oil it all very well and take care not to cut the seals. If you try without the shim stock, the threads usually do a number on the seal. If it doesn't leak right away, it's service life will be much reduced. Don't ask me how I know.

Good Luck,
Terry
stephenc
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Re: Give me the Bad News on Hydraulic Seal Leaks

Post by stephenc »

One thing no one had addressed is possible reasons why it's leaking.
If it's just a bad seal , no big deal .

But you should also be looking for rust pitting or chrome flaking off . If either is the case a new seal is going to be a short term fix at best .
If you do have rust pits or flaking chrome sending it out to be turned and rechromed might be an affordable option if there is anyone in your area that rebuilds cylinders .
Or you might be able to find a new cylinder for fairly reasonable money if you shop around . .. smaller cylinders really aren't that expensive in the grand scheme of things .

And as mentioned above .... if you have it apart re-pack it while your at it .


But all that just addresses a leaking cylinder ,... there are many many many other things to leak then the cylinder , first thing to address is finding the actual leak itself .
I'd almost bet money that it is something other then a cylinder leaking .
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SteveHGraham
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Re: Give me the Bad News on Hydraulic Seal Leaks

Post by SteveHGraham »

It was hard to find anyone to check the machines, but I finally located a guy who claims he has all sorts of certifications. For a hundred bucks, he's going to inspect them. Here's hoping for the best.
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warmstrong1955
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Re: Give me the Bad News on Hydraulic Seal Leaks

Post by warmstrong1955 »

And if he knows much of anything, he can tell you what seal is leaking, and why...

:)
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SteveHGraham
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Re: Give me the Bad News on Hydraulic Seal Leaks

Post by SteveHGraham »

He did not sound worried at all.

Or course, he's going to get paid either way, so what does he have to worry about? But he did say Kubotas were tough.
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warmstrong1955
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Re: Give me the Bad News on Hydraulic Seal Leaks

Post by warmstrong1955 »

We used a lot of Kubotas in the mines, although larger than what you are lookin' at. Mostly transportation, but had many with loader front ends with a quick attach for a bucket or forks, and sometimes short jib booms. Handy critters, and they required little above routine maintenance.

If they'll hold up in a mine, they should last a kazillion years for a home owner! (Rule of thumb)

Bill
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SteveHGraham
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Re: Give me the Bad News on Hydraulic Seal Leaks

Post by SteveHGraham »

Here is the bad news: the John Deere needs a cheap seal on the PTO, which I can install myself, and the Kubota leak is coming from...a quick coupler. Color me happy.

The mechanic says the machines are worth a lot more than I'm paying. I think this will be the first time in my life I've bought something motorized without getting screwed.

Good thing I passed on all the Clausing tractors I looked at.

Now I have to look into tractor umbrellas.
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